feat: agent memory (beta) docs (#31086)

* feat: agent memory docs

- Add product directory entry (agent-memory.yaml) and SVG icon
- Add product overview page with features, related products, and resource links
- Add get-started guide: create namespace, configure binding, ingest/recall/summary
- Add concepts: how Agent Memory works (extraction, classification, dedup, storage, recall pipeline, memory types, idempotency) and profiles/namespaces isolation model
- Add configuration page for memory_namespaces Worker binding (single and multiple bindings, TypeScript types)
- Add API reference: ingest() with Message type, timestamps, and idempotency; recall() with thinking levels, response length, and reference date; getSummary() with session scoping and summary structure
- Add namespace management REST API reference (create, list, get, delete)
- Add platform pages: validation limits and naming constraints, beta pricing placeholder
- Add example: chat agent with memory using Workers AI (ingest, recall, getSummary in a conversation loop)

* fix: correct code examples and docs for agent memory docs

* Apply suggestions from code review

Co-authored-by: devin-ai-integration[bot] <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* Refine Agent Memory docs and API reference

* Update the docs with latest changes

* Update the get started code

* Add Agent Memory to sidebar

* Update types and apply review comments

* Add team members as code owners

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Co-authored-by: Payam Mesgari <payam@cloudflare.com>
Co-authored-by: Pete Bacon Darwin <pete@bacondarwin.com>
Co-authored-by: devin-ai-integration[bot] <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Phillip Jones <pjones@cloudflare.com>